There are well-documented disparities in vaccination rates between different socioeconomic and racial/ethnic groups in the United States. These disparities persist in spite of an overall increase in vaccination rates during the last decade and the implementation of several interventions that have aimed to increase vaccination rates in disadvantaged groups. Although many interventions are efficacious at improving vaccination rates under trial conditions, these interventions when extended to the general population frequently do not appreciably improve its health. Explanations for this limited intervention efficiency include poor adherence to protocols in real life versus idealized trial situations, changes in baseline so that the trial conditions are no longer replicable, and the contribution of other community-level factors that make it difficult to extend the trial methods to other communities. Multilevel community intervention trials recognize and address the multiple competing forces that shape the health of the population in cities and have the potential to increase vaccination rates among minorities and marginalized groups.